Cobalt dicarbonyl

For instance, the (pentaphenylcyclopentadienyl) cobalt dicarbonyl anion-radical complex [(q-C5Ph5)Co(CO)2] has (n + 1) metal orbital populated with an unpaired electron, according to calculations by Connelly et al. (1986). In contrast, reduction of (bpy)Cr(CO)4 (bpy = 2,2 -bipyridyl) to its anion radical is known to occur without any major change in its structure or composition. 

In a similar manner, silacyclopentadienes react with cyclopentadienyl-cobalt dicarbonyl to give an - -complex (49, 138) ... 

Cobalt Dicarbonyl-pentafluorophc-nyl-(74-tetrapbenyl-cyclopenta-dienyl)- XIII/9b, 32 [F5C -Li + R(CO),CoBr]... 

Reaction of thietes with iron carbonyls or cyclopentadienyl cobalt dicarbonyl affords thioacrolein complexes 57 and 58. On gentle heating or... 

The annelated pyridine is also obtained with / -Cp-cobalt dicarbonyl as catalyst [43]. Using this variant of the cobalt-catalyzed cycloaddition, Schleich and co-workers [44] opened up a new route to pyridoxine (vitamin B ) as its hydrochloride (eq. (15)). 

Applying the versatility of the cobalt-catalyzed pyridine formation (eq. (2)), Vollhardt [45] has varied the basic reaction extensively. Using rather sophisticated alkyne and nitrile precursors with 77 -Cp-cobalt dicarbonyl as the catalyst, the preparation of a number of polyheterocyclic systems having physiological interest was brought about. Using eq. (14) a synthetic route to the isoquino[2,l-(7] [2,6]naphthyridine nucleus (eq. (16)) was developed [46]. 

The reaction according to eq. (25) leads exclusively to cw-hexahydronaph-thalene (cw-hexaline), a product which is otherwise accessible only by multistep synthetic pathways [72], Macomber [73] reported the [2+2+2] cycloaddition reaction of diphenylacetylene or C2(C02Me)2 and ntfo-dicyclopentadiene or norbomylene, respectively, in the presence of -Cp-cobalt dicarbonyl or -methyl-Cp-cobalt dicarbonyl in refluxing toluene. 

Intramolecular cyclohexadiene syntheses have been developed by Vollhardt [74], Enediynes with a terminal double bond react in isooctane at 100 °C in the presence of -Cp-cobalt dicarbonyl giving a three-ring system [75] according to eq. (26). 

The formation of the jf-c omplexes (Eq. 6) is disfavored by the introduction of bulky substituents at the a-positions of the phosphole ring. For example, rf-phospholyl-cobalt-dicarbonyls can be synthesized only with a-substituents such as phenyl [14] or tert-butyl [15]. In order to avoid redox reactions (Eq. 7), it may be necessary to replace the phospholide ions by tin [16] or lead derivatives [17] (Eqs. 8,9) ... 

Acylcobalt carbonyl derivatives are cleaved by sodium methoxide to esters and sodium salts of the corresponding carbonyl anions. By means of this reaction, acetyl[bis(trimethylolpropane phosphite)]cobalt dicarbonyl has been converted into sodium [bis(trimethylolpropane phosphite)]cobalt dicarbonyl. The latter compound is readily alkylated by methyl iodide to form the methylcobalt derivative and this compound in turn reacts with another mole of the phosphite ester, in the same way that methylcobalt tetracarbonyl does, to form acetyl[tris(trimethylolpropane phosphite)]-cobalt carbonyl ... 

The last-mentioned compound does not react further with triphenylphos-phine, but it does with trimethyl phosphite, forming acetyl(trimethyl phosphite)(triphenylphosphine)cobalt dicarbonyl (10). 

With a large excess of trimethyl phosphite, the triphenylphosphine is replaced, forming acetyl[bis(trimethyl phosphite)]cobalt dicarbonyl. The bis- and tris(phosphite) derivatives of acetylcobalt tetracarbonyl are more thermally stable and more resistant to air oxidation than are the monophosphite or triphenylphosphine derivatives. 

The diene insertion reaction will take place intramolecularly if the diene system is part of the acyl group in the acylcobalt tetracarbonyl (13). Thus, /ra j-2,4-pentadienoyl(triphenylphosphine)cobalt tricarbonyl, prepared by the acid chloride method, cyclizes on heating in ether solution in a closed vessel at 75° C for an hour, to 7r-cyclopentenonyl(triphenylphosphine)cobalt dicarbonyl in 30% yield. 

Treatment of Na[Co(CO)4] with methyl iodide and trimethylphosphite gives the cobalt dicarbonyl CH3COCo(CO)2[P(OCH3)3]2... 

C12H12CO2O4, Butadiene cobalt dicarbonyl, 31B, 346 Cl2H12Ni2, M Acetylene-bis(cyclopentadienylnickel), 42B, 658 Cl2H120bW, trans-Bis(772-methyl acrylate)tetracarbonyltungsten, 46B, 838... 

Toluene and THF were distilled from sodium benzophenone ketyl before use. Tantaliun bromide, niobiiun bromide, niobium chloride, cyclopentadienyl cobalt dicarbonyl, bis(l,5-cyclo-octadiene)diiridium(I) dichloride, tetraphenyltin, and tri-phenylphosphine were Aldrich products of the highest purities. All other reagents and solvents were purchased from Aldrich and used as received. 

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